1. Field of the Invention
The present invention relates to the production of metal pipe, and more particularly, to the production of cast ductile iron pipe with bell ends formed using sand cores, and to a system for removing the sand cores from the cast pipe before the pipe is heat treated.
2. Description of the Prior Art
In the production of objects such as elongate cast metal pipes, centrifugal casting has been commonly used. In such a casting operation, the pipe is cast in a cylindrical mold. Molten metal, such as iron, is fed into the mold through a trough. The trough has a spout at one end which is curved toward the sidewall of the mold. A sand core is inserted into the bell end of the mold to form the inside contour of the pipe bell. The bell end of the pipe""s inside contour typically includes one or more annular grooves or depressions defining a gasket seat area to receive a gasket. The mold is rotated and once it is brought up to the appropriate speed, molten metal is poured into the trough. Once the bell end of the pipe has formed, the mold is moved horizontally while rotating. The stream of molten metal discharged from the spout flows tangentially onto the surface of the mold, where it is held in place by centrifugal force. The molten metal forms a homogeneous pipe with a cylindrical bore.
After the pipe has been completely cast, the mold is kept rotating until the pipe has cooled to a desired temperature. The pipe must then be taken from the casting machine and transferred to a heat treating furnace. In some instances, the sand cores are not removed from the cast pipe before annealing; instead, the sand core is allowed to disintegrate at the temperatures in the annealing oven. However, in other types of production, it is desirable to remove the sand core from the bell end of the pipe before the pipe enters the heat treating furnace. This removal of the sand core is particularly important in plants in which the pipe is set vertically and supported on its bell end in the heat treating furnace; remnant pieces of the sand core could cause the pipe to be off-balance in the furnace, and risks toppling of the pipe.
Traditionally, the sand cores have been manually removed. In the manual process, a worker hits the sand core with a hammer to break the core into smaller pieces, and then scrapes out the pieces of the core using a hoe-type of tool. However, this process has required the worker to be in close proximity to the hot pipe, and has been time consuming, adding to the expense of producing cast iron pipe.
The present invention addresses the problem of removing sand cores from the bell ends of cast metal pipes in an efficient manner.
In another aspect, the present invention provides a system for removing a sand core from a cast iron pipe in a plant for making ductile iron pipe. The ductile iron pipe has a bell end, a hollow interior and an interior surface. The plant has a casting station for casting the iron pipe with a sand core to define the shape of at least a part of the interior surface of the pipe at the bell end of the pipe. The plant also has a heat-treating station downstream from the casting station to heat treat the pipe. The system for removing the sand core is positioned so that the sand core is removed before the cast pipe reaches the heat-treating station. The sand core removal system includes a brush assembly and an exhaust system. The brush assembly includes a shaft with a central longitudinal axis and a brush mounted on the shaft. The brush assembly is rotatable about the central longitudinal axis of the shaft to clean core sand from the pipe. The exhaust system is positioned to draw core sand away from the pipe after the core sand has been cleaned from the pipe. The exhaust system includes a hood. At least part of the brush is positioned within the hood.